Switch assembly



Sept. 6, 1961 D. w. LAVIANA 3,002,000

- SWITCH ASSEMBLY Filed May 24, 1960 34 I 2 5O 74 22 24 70 66 59 38 283o '8 l8 64 62 36 32 as so 6 l4 .2 l

Hg; ,3 INVENTOR.

Donald W Lav/emu.

His Aflomey United States Patent Patented Sept. 26, 1961 3,002,060SWITCH ASSEMBLY Donald W. Laviana, Pittsford, N.Y., assignor to GeneralMotors, Corporation, Detroit, Mich, a corporation of Delaware s FiledMay 24, 1960, Ser. No. 31,372 11 Claims. (Cl. 200-'-38) 'Ihisinventionpertains to switches, and particularly to an improved switch assembly ofthe cam operated type. The present application is a continuation in partofmy copending application Serial No. 786,953 filed January 15, 1959. I

Heretofore the. majority of cam' operated sequence switches .used intimers for controlling appliances, such as washing machines, haveembodied integral leaf spring contact assemblies. In the design of camoperated sequence switches, several factors must be considered, amongthese being the following: to provide a switch element requiring aminimum torque at its operating cam; to provide a switch'element havinga high initial contact pressure when it is disengaged from its operatingcam and engages one fixed contact; and to require a minimum ofadditional force to move the switch element into engagement with anotherfixed contact and provide sufficient contact pressure with a minimum ofadditional deflection.

'The present invention relates to a switch assembly including leafspring blades, or reeds, having a low forcedeflection gradient, the leafspring blades being prestressed in one direction so as to have twospring rates. Accordingly, among my objects are the provision of animproved leaf spring switch assembly for timers; the furtherprovision=of a leaf spring switch assembly having aseparate ca'mfollower member attached thereto in such a manner so as to bend theintermediate portion of the leaf spring in the direction of itsinitialprestressing; the further provision of an improved leaf springswitch assembly of the aforesaid type having a low springrate inthedirection "of the prestressing and a high spring rate in'the oppositedirection; and the further provision of a switch assembly including aleaf spring blade designed to accommodate substantial over-travelwithout exceeding the yield point of the material and, therefore,avoiding permanent deformation of the leaf spring blade.

' The aforementioned and other objects are accomplished in the presentinvention by prest'ressing the leaf spring blades adjacent their pointsof attachment to a base and attaching a saddle member thereto at theintermediate portion of each leaf spring to further prestress each leafspring in the direction of its initial'prestr'essing. Specifically, theswitch assembly includes a base, or terminal block, having a pluralityof terminals attached thereto. One end of each leaf spring blade isstaked, or otherwise rigidly attached, to a terminal, and the other endof each leaf spring blade carries a contact on each side thereof. Oneset of the spring blade contacts are engageable with a first set offixed contacts attached to one set of terminals, and the other set ofblade contacts are engageable with a second .set of fixed contactsattached to another set of terminals andspaced from the first set offixed contacts. A saddle member, or harness, is attached to theintermediate portionof each leaf spring blade.

The saddle member is composed of insulating material tooth-type camfollower projecting from the upper side thereof. The saddle member isformed with a pair of openings on opposite sides of. the projecting camfollower tooth through which a leaf spring blade can be threaded. Eachleaf spring blade is formed with a reinforcing bead adjacent the'contactend thereof and a circular hole in the medial portion, the circular holebeing adapted to reand comprises a generally rectangular member having aceive an integral nub, or stud, formed on the saddle member. The saddlemember has transversely extending rails at each end thereof and theintegral stud projects downwardly from the lower surface of the cam;follower projection. The surface on which the stud is formed issubstantially parallel to and spaced above the upper surface ofthe'inner end rail, and the outer end rail is located in a plane spacedabove the surface on which the stud is formed such that the leaf springblade will be bent as it is threaded through the openings and attachedtotthe saddle member. More particularly, the leaf spring blade will-bebent in the same direction as its initial p'restressing by itsattachment to the base.

By bending the intermediate portion of each leaf spring blade, each leafspring blade is additionally prestressed to obtain the requisite contactpressure between the leaf spring blade contacts and the fixed contactsclosest to the cam. The leaf spring blades have low spring rates, or arevery limp, when bent in the same direction as the direction of theprestressing, and have high spring rates, or'are very stiff, and thusresist bending in'the opposite direction. The stiffening bead adjacentthe contact end of each leaf spring prevents bending of the leaf springsdue to initial prestressing, or preloading, against the fixed contactsclosest to the cam. Only a small additional force is required to movethe reed into engagement with the fixed contacts spaced farthest fromthe cam, and after engagement of the leaf spring blades with the latterset of fixed contacts the requisite contact pressure is achieved bybending the spring blades in the direction of their prestress, which dueto the low spring rate of theblades in this direction, requires aminimum force. This low spring rate enables the switch assembly toaccommodate substantial overtravel without exceeding the yield point ofthe spring blade material and thus avoids premanent deformation.

While the embodiment of the inventionas herein disclosed constitutes apreferred form, itis to be understood that other forms might be adopted.1

In the drawing: FIGURE 1 is a plan view of a switch assembly constructedaccording to the present invention.

FIGURE 2 is a sectional view taken along lines 22 'of' FIGURE 1 showinga segment of an actuating cam with the leaf spring blade engaging afixed contact closest to'the cam.

FIGURE 3 is a view similar to FIGURE 2 showing thev leaf spring bladeengaging the fixed contact farthest from the cam;

FIGURE 4 is a perspective view of the novel cam follower member, orsaddle.

With particular reference to FIGURES 1 through 3, the switch assemblyincludes a base, or terminal block, 10 of insulating material havingspaced sets of spadetype' terminals 12, 14 and 16 molded therein. Thesets of terminals 12, 14 and 16 project from both sides of the base 10and have staking lugs 18 located on the upper side of the base. Asdepicted in FIGURES 2 and 3, a set of substantially S-shaped Phosphorbronze strips 20'are staked to the set of terminals 14, and a second setof substantially S-shaped Phosphor bronze strips 22 are staked to theset of terminals 16. The strips 20 carry fixed contacts 24 which arelocated in a planeinclined to the base 10, and the strips 22 carry fixedcontacts 26 which are locatedin a plane substantially parallel to andspaced from the plane of the contacts 24.

The switch assembly also includes a plurality of Phosphor bronze leafspring blades, or reeds, 28. The inner end of each leaf spring blade isstaked to one of the terminals 12 and is transversely bent along a lineindicated generally by the numeral 30 so that the outer end of each leafspring blade is prestressed, or preloaded,

thereof engageable 3 towards the fixed contact 26; The outer endof-each-leaf spring blade carries contacts 32 and 34 on opposite sidesrespectively with fixed contacts 24 and 26. V

' :The intermediate portion of each leaf spring blade '28 has-a circularhole 36 formed therein. Asaddle member, or harness,"38,-such as depictedin-FI GURE 4, is assembled with each leaf spring blade and is attachedto the medial portion thereof. The saddle-members 38 are composed ofinsulating material, 'such as a phenolic condensation product, andcomprise side rails 40- and- 42, end

rails.44. and 46, and anintermedia-te web 48 having an upstanding'toothed-type cam follower 50. A generally rectangular opening 52. isformed between the web 48 and --end. rail 44, and .a second generallyrectangular opening 54 is formed between the cam follower tooth 50 andthe end rail 46. I i

As seen particularly in FIGURES 2 and 3,. the upper surface 56. of theendrail 44 and a portion 58: of the :lowernsurface of web 48.1ie insubstantially parallel planes. with the portion 58. spaced above. thesurface 56. The. end rail .44 is formed with a charnfered inner edge.60,- ,andi'the portion-5.8 of the lower surfaceof the web =48 gisformed. .withlanintegral downwardly projecting nub,

I :orstud, 62. The lower surface 64 of the cam follower s-tQoth-JSO. isinclinedupwardly with respect to the lower :surfacesof the sidetrails 40and 42. The upper surface =66, of,;end rail. 46,,is located in a planesubstantially parallel .tobutfspaced above both the upper surface 56 ofthe. end rail 44 and the lower surface 50. of the web .48.

The inneredge ofend rail 46 is, fo'rmedwith a chamferedq-portion168,which extends in a direction opposite to, the chamfered, edge 60'.

The saddle member .3 8 -is assembled with the leaf spring 7 blade 28 bythreading the inner end thereof through the lope lillg .54 and throughthe opening 52. prior to attachment of-the inner end to the terminal 12.When the ,.stud .62. is aligned with-the circular hole 36 in the leafspring, the diameter of the stud being substantially the ..'same as thediameter of the opening 36," the saddle mem- ':;ber 38 will be securelyattached to the leafspringblade 28. In threading the leaf spring bladethrough the openings 54 and 52, the lower surface of the leaf springblade .engages the upper surfaces 56 a d. of the end rails 44 and 46respectively, and the lower surface portion 58 ,of. the web 48, wherebythe medial portion of the leaf springblade will be bent intermediate itsends in the. same direction as the prestressing bend 30.

As 'seen particularly in FIGURES 1 through-3, each A leaf springblade isformed with a reinforcing bead 70 adjacent, its outerend. Thereinforcing 'beads 70, stiffen the leaf spring blades in the directionof; the prestress and prevent deflection of each leaf spring blade 28-due to engagement with the fixed contact 34.

The. cam follower tooth 50 is adapted to be engaged by a; rotating cam72,. a fragmentary portion of which :is depicted in FIGURES 2 and 3. Thecam 72 may inl-cludea plurality of; rises '14, and dwells 76 suchthatwhen the-follower 50 engages a rise -74. the leaf spring blade .28 willbe moved into engagement with fixed contact 24,

an'dwhen the-followenSt}lisaligned with. a dwellld the leaf spring blade.28..will engage. the fixed contact 26.

@When the. follower 5.0 engages-a portion of the cam/7 2 between'therise74.and thedwell 76, the contacts carried by .the leaf spring blade willengage neither contact 24.nor

contactv 26. The leaf spring blades 28. are prestressed or preloaded ina direction to engage the fixedcontacts 26 which, clearly seeninthedrawing, are located. closest to the cam'72; The fixed contacts 24,on theotherhand,

7 prehea ed-farthest. from-the earn .2- r

"Th le -f pringfjblj de Zahara in effec wo spring rate by vi tu 'of thfp estres n y' he bend 30 and the intermediate bendby the. saddlememb'er. 3z3. In otherfword's, the-leaf spring blades, 28 .ha'vea lowspring rate, or are easily flexed, in the direction of tl'ieprestressthat is towards the fixed contacts 26which are closest to I d the cam72. However, the leaf spring blades have a high spring rate, or are verystiff, and thus resist bending in the opposite direction. In thismanner, the high contact reaction force when the switch blade contacts34 engage 1 38, to the position of engagement with the fixed contacts26. The contact pressure at the'fixed contacts 24 isthe force necessaryto bend the spring blades to their final curvature supported at theirattachments tothe-base, the contacts 24, and the surface 58 of thesaddle member-38.

It is pointed out that the leaf spring blades are disengaged from thesurface 66 of the saddle member only during overtravel when the contacts32 engage fixed contacts 24-. The leaf spring blade engages thesurface66 of the saddle member when the spring blade is suspended between the,

contacts 24 and 26 as well as when the contact 34 engages fixed contact26.

During rotation'of the cam 72 in the direction of the arrow in FIGURE 2,the cam follower 50 will be engaged by the cam surface so as, to movethe leaf spring blade28 towards the base 10 and disengage leaf springcontact 34 from fixed contact 26. At this time the leaf spring blade issuspended between the fixed contacts 26 and 24 while constrained withinthe saddle member 38.,- When the cam fol-lower 50 engages the rise 74.on the cam 72, the :contact 32 will engage the fixed'contact' 24. :Onlya minimum force is required to move the switch blade from engagementwith contact 26 to engagement with contact 24. After engagement of leafspring contact'32 with fixed contact 24 the requisite contact pressureis obtained by bending the medial portion of the leaf spring springblade 28 in the direction of its prestress as seen in FIGURE 3. Sincethe spring blade28 has, a'low spring, rate in this direction, itrequires very little: additional force to obtain the requisite contactpressurebe tween the leaf spring blade contact-32and the fixed contact24. By enablingthe leaf spring blade 28 to. bend 7 intermediate itsendsand become disengaged from the upper surface, 66 of the end rail 46,overtravel can be accommodated without stressing the spring blade beyondits elastic limit thereby avoiding permanent deformation.

While the embodiment of the invention as herein disclosed constitutes apreferred ,form, it; is to be understood that other forms might beadopted.

What is claimed is as follows:

1..A cam'operated switch including,'a base, a leaf spring having one endattached to said base; and prestressed adjacent its attachment in onedirection, and a member attached to said leaf spring so asto bend themedial portion thereof in said one direction whereby said leaf springhas a low spring rate in said one direction and a high springv rate inthe opposite direction.

contactsupported on said base in spaced relation thereto, -a leaf springhaving one end attached to said baseand prestressed adjacent itsattachment towards said fixed contact, and a member attached to saidleaf spring so as to bend the medial portion thereof towards saidiixedcontact whereby said leaf spring has a low spring rate: in the directionof said prestressing and a highspring.

rate inthe opposite direction.

3. A cam operated switch including; a base, a fixed contact attached tosaid base in spaced relation thereto, a leaf spring having one endattached to said' base and prestressed adjacent its attachment in adirection away from said fixed contact, and a member attached to saidleaf spring so I as to bend the medial portion'thereofin .a directionaway from said fixed contact wherebysaid leaf spring has a low springrate in the direction away 2. A camoperated switch includingalbase; afixed from said fixed contact and a high spring rate in a directiontowards said fixed contact.

4. A cam operated switch including, a base, first and second fixedcontacts attached to said base in spaced relation thereto and in spacedrelation from each other, a leaf spring having one end attached to saidbase and prestressed adjacent its attachment towards one of said fixedcontacts, the other end of said leaf spring being disposed between saidfixed contacts, and a member attached to said leaf spring so as to bendthe medial portion thereof in the direction towards said one fixedcontact whereby said leaf spring has a low spring rate in the directionof said one fixed contact and a high spring rate in the ppositedirection. I V

5. The cam operated switch set forth in claim 4 including a camengageable with said member for moving said leaf spring in the oppositedirection into engagement with said other fixed contact, the arrangementbeing such that when said leaf spring engages said other fixed contactsaid leaf spring is deflected in the direction towards said one fixedcontact.

6. A cam operated switch including, a base, a leaf spring having one endattached to said base and prestressed adjacent its attachment in onedirection, said leaf spring having a reinforcing bead adjacent its otherend, and a member attached to said leaf spring so as to bend the medialportion thereof in said one direction whereby said leaf spring has a lowspring rate in said one direction and a high spring rate in the oppositedirection.

7. A cam operated switch including, a base, a fixed contact supported onsaid base in spaced relationship I thereto, a leaf spring having one endattached to said base and prestressed adjacent its attachment towardssaid fixed contact, and a saddle member having end rails, anintermediate web and spaced openings between said web and said endrails, said leaf spring being threaded through said openings so as tobend the medial portion thereof towards said fixed contact whereby saidleaf spring has a low spring rate in the direction of said prestressingand a high spring rate in the opposite direction, said leaf springhaving a reinforcing bead adjacent its outer end for preventingdeflection of said leaf spring due to engagement with said fixedcontact.

8. The switch assembly set forth in claim 7 wherein said leaf spring hasa circular hole in the medial portion thereof.

9. The switch assembly set forth in claim 8 wherein said saddle memberis formed with a projecting stud on said intermediate web, and whereinsaid stud extends through the circular hole in said leaf spring.

10. The switch assembly set forth in claim 7 wherein the lower surfaceof said leaf spring normally engages the upper surfaces of said endrails, wherein the upper surface of said leaf spring engages the lowersurface of said intermediate web, and wherein the upper surfaces of saidend rails and the lower surface of said web are located in spacedparallel planes.

11. The switch assembly set forth in claim 10 wherein the inner edges ofsaid end rails are chamfered in opposite directions.

References Cited in the file of this patent UNITED STATES PATENTS1,092,266 Howe Apr. 7, 1914 2,204,949 Richie June 18, 1940 2,559,568Hooven July 3, 1951 2,856,473 Bell et al. Oct. 14, 1958

